theorem bian11da (G a b c d: wff): $ G /\ d -> (a <-> b /\ c) $ > $ G -> (a /\ d <-> b /\ (c /\ d)) $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | anass | b /\ c /\ d <-> b /\ (c /\ d) |
|
2 | hyp h | G /\ d -> (a <-> b /\ c) |
|
3 | 2 | aneq1da | G -> (a /\ d <-> b /\ c /\ d) |
4 | 1, 3 | syl6bb | G -> (a /\ d <-> b /\ (c /\ d)) |